Human soft tissue sarcomas are malignant tumors arising in the extraskeletal connective tissues of the body. For the past several years we have been involved in producing murine monoclonal antibodies (MAbs) to cell surface sarcoma-associated antigens and have generated 16 MAbs defining 9 antigenic systems. In this proposed continuation project we intend to identify those MAbs which have potential clinical usefulness in the diagnosis of this diverse group of tumors and in improving therapy. The specific aims of this research proposal are: 1) To perform a complete binding specificity analysis on all MAbs produced. Specificity testing will be done on membrane preparations of fresh surgical tissues, cultured and fresh cells, tissue sections, and biochemically-characterized antigens. 2) To continue to produce MAbs to sarcoma-associated antigens. We will use protocols optimized during our present study as well as new approaches designed to generate MAbs with broad sarcoma specificity, sarcoma subtype specificity, and specificity for shed antigens. 3) Analysis of MAb immunohistochemically results with tissue sections for utility in aiding pathologic diagnosis. The MAbs will be assessed for ability to discriminate tumor from normal, sarcoma from nonsarcoma, different sarcoma subtypes, and degree of differentiation (grade). 4) Use of MAbs against shed antigens for the detection and quantitation of tumor markers in sera of sarcoma patients. Marker levels will be correlated with tumor burden, surgery, response to therapy, and clinical course. 5) Analysis of radiolabeled MAbs in a human sarcoma xenograft- athymic mouse model for ability to localize to tumor after in vivo administration. These studies will focus on MAbs with high binding constants for cell surface sarcoma-associated antigens. 6) Analysis of the therapeutic activity of MAbs and MAbs conjugated with chemotherapy drugs when tested in vitro and in the athymic mouse model. These studies will focus on MAbs identified in Specific Aim 5 as showing significant in vivo tumor localization. Our long-term goals involve the clinical application of the MAbs in pathologic diagnosis, prognosis, monitoring clinical course, and therapy. MAbs identified in this project may be entered into our on-going clinical tumor imaging studies.